It's not funny. Not in its current state.
It's a big "Sorry" pawn that eats custard. The custard is produced by memetic clay (that's not what memetic means) that travels between planets and turns into bowls of custard. The pawn follows the dust and eats custard and/or manifests in ordinary custard. And there is use of spanking "barebutt style" as a punishment, which is wholly unclinical. Aside from format screws, the Foundation generally keeps their scientific tone when documenting joke SCPs. The joke is primarily the SCP, not the way in which the Foundation deals with it or contains it. The phrase "mentally retarded" in this context feels more perjorative than literal, additionally, as though you say it yourself in real life. Not cool.

I can't help but feel this is a pop-cultural character I've somehow not yet encountered. Like those cereal mascots who never get their cereal. Actually, if you went that route, and made this a fictional custard mascot come to life trying to get his custard, that might be pretty funny. So far as I can tell, the situation is unique. Although I advise against having the pawn "maul and messily ingest" the -B. That's both cheap gore and not within the modus operandi of a kid's product mascot.

Lose the talk about "Internet memes." That line is both irrelevant, bad tone and it's out of character.